字节输入流/输出流

package cn.lianxi.test;

import org.junit.Test;

import java.io.*;
import java.nio.charset.StandardCharsets;


public class Demo {
    @Test
    public void test01() throws Exception {
        File file = new File("file1.txt");

        //如果不存在 就创建
        if(!file.exists()){
            file.createNewFile();
        }
        //创建in输入流
        FileInputStream in = new FileInputStream(file);

        int i = -1;
        while ((i = in.read()) != -1){
            System.out.println((char)i);
        }

        in.close();
    }

    @Test
    public void test02() throws Exception {
        //创建out输出流                 append参数: 默认不写是false,改为true可追加写入
        FileOutputStream out = new FileOutputStream("file1.txt",true);
        //方式一
//      out.write(97);
//      out.write(97);
//      out.write(97);
        //方式二
//      byte[] bytes = {12,23,45,56,63};
//      out.write(bytes);
        //方式三
        byte[] bs1 = "abcdefg".getBytes(StandardCharsets.UTF_8);
        out.write(bs1,0,3);//从索引off开始，写length个字节

        for (int i = 0; i < 5; i++) {
            out.write("hello".getBytes(StandardCharsets.UTF_8));
            //换行的三种方式
            out.write("rn".getBytes(StandardCharsets.UTF_8));
            //out.write("n".getBytes(StandardCharsets.UTF_8));
                //out.write("r".getBytes(StandardCharsets.UTF_8));
        }
            out.close();
    }

    @Test
    public void test03() throws Exception{
        
        //创建out输出流
        FileOutputStream out = null;       //append参数: 默认不写是false,改为true可追加写入
        try {
            out = new FileOutputStream("file1.txt", true);
            //方式一
            out.write(97);
            out.write(97);
            out.write(97);
        }catch (IOException e){
            e.printStackTrace();
        }finally {
            if(out!=null){
                try {
                    out.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    @Test
    public void test04() throws Exception {
        
        File file = new File("file2.txt");
        //如果不存在 就创建
        if(!file.exists()){
            file.createNewFile();
        }
        //创建字节输入流
        FileInputStream in = new FileInputStream(file);
        //从这个输入流读取一个字节的数据。
        int read = in.read();
        System.out.println("read = " + read);
        in.close();
    }
    @Test
    public void test05() throws Exception {
        
        File file = new File("file3.txt");
        //如果不存在 就创建
        if(!file.exists()){
            file.createNewFile();
        }
        //创建字节输入流
        FileInputStream in = new FileInputStream(file);
        //从这个输入流读取一个字节的数据。
        int read = in.read(); //int read ;
        while(read != -1){    //while((read = in.read) != -1)
            System.out.println((char)read);
            read = in.read(); //
        }
        in.close();
    }
    @Test
    public void test06() throws Exception {
        
        File file1 = new File("file2.txt");
        if(!file1.exists()){
            file1.createNewFile();
        }
        File file2 = new File("file3.txt");
        if(!file1.exists()){
            file1.createNewFile();
        }
        FileInputStream in = new FileInputStream(file1);
        FileOutputStream out = new FileOutputStream(file2);

        int bys; //实际写入的字节数
        //设置一个
        byte[] bytes = new byte[1024];
        while((bys = in.read(bytes)) != -1){
            out.write(bys);
        }
        out.close();
        in.close();
    }

}